As a kind of a one-way clutch that is assembled in a pulley apparatus for driving an auxiliary machine for an automobile, such as an alternator or starter motor, there is a roller clutch. A pulley apparatus that is equipped with a roller clutch in which this kind of roller clutch is assembled has been known such as disclosed in JPH07072585 (B), JPH11063170 (A), JP2002130433 (A), JP2005003059 (A), and JP2007198582 (A). FIG. 12 to FIG. 14 illustrate an example of a conventional pulley apparatus that is equipped with a roller clutch. The pulley apparatus 1 equipped with a roller clutch has a sleeve 2 that can be fitted around and fastened to the rotating shaft of an alternator. A follower pulley 3 is arranged around this sleeve 2 and is concentric with the sleeve 2. There is a pair of support bearings 4 and a roller clutch 5 located between the outer-circumferential surface of the sleeve 2 and the inner-circumferential surface of the follower pulley 3.
The sleeve 2 is formed into an overall cylindrical shape, is fastened around the end of the rotating shaft of the alternator, and rotates together with this rotating shaft. Moreover, a large-diameter section 6 having a larger outer-diameter dimension than both end sections of the sleeve 2 is provided in the center section of the outer-circumferential surface of the sleeve 2. On the other hand, the cross-sectional shape in the width direction of the outer-circumferential surface of the follower pulley 3 is a wave shape so that part of a continuous belt called a poly V belt can pass around the pulley 3. A roller clutch 5 is located in the middle section in the axial direction of a space located between the outer-circumferential surface of the sleeve 2 and inner-circumferential surface of the follower pulley 3, and a pair of support bearings 4 are located on both end sections in the axial direction of this space and on both sides in the axial direction of the roller clutch 5. The pair of support bearings 4 allow relative rotation between the follower pulley 3 and sleeve 2, while supporting radial loads that are applied to the follower pulley 3. In the example illustrated in the figures, a deep-groove ball bearing is employed for both of the support bearings 4.
The roller clutch 5 allows to transmit torque between the follower pulley 3 and sleeve 2 only when there is a tendency for the follower pulley 3 to rotate in a specified direction with respect to the sleeve 2. The roller clutch 5 has a clutch inner ring 7, a clutch outer ring 8, plural rollers 9, a retainer 10, and plural springs 11.
The clutch inner ring 7 and clutch outer ring 8 are each formed into an overall cylindrical shape using a plate member made of hard metal such as bearing steel or the like, or of carburized steel such as SCM415 or the like. The clutch inner ring 7 is fitted around and fastened to the outer-circumferential surface of the large-diameter section 6 of the sleeve 2 by an interference fit, and the clutch outer ring 8 is fitted around and fastened to the inner-circumferential surface of the middle section of the follower pulley 3 by an interference fit. Moreover, at least the middle section in the axial direction of the inner-circumferential surface of the clutch outer ring 8 that comes in contact with each of the rollers 9 is a cylindrical surface 12. On the other hand, by forming plural concave sections 14 called ramp sections on the outer-circumferential surface of the clutch inner ring 7 so as to be uniformly spaced in the circumferential direction, the outer-circumferential surface of the clutch inner ring 7 becomes a cam surface 13.
The retainer 10, plural rollers 9 and plural springs are arranged in the cylindrical space between the cylindrical surface 12 and cam surface 13. The retainer 10 is integrally formed into a cage-like cylindrical shape by a synthetic resin such as polyamide 46, and has a pair of ring-shaped rim sections 15 respectively having an annular shape and plural column sections 16 that are uniformly arranged in the circumferential direction of the retainer 10 and connect the portions near the inner-circumferential edge of the inside surfaces of the rim sections 15. Plural protruding pieces 17 that are formed on the inner-circumferential surfaces of the rim sections 15 engage with the plural concave sections 14 of the cam surface 13, which makes it impossible for the retainer 10 to rotate relative to the clutch inner ring 7.
A pair of rear support plate sections 18 that are continuous with the inside surfaces of each of the rim sections 15, and that protrude outward in the radial direction from the outer circumferential surface of each of the column sections 16 are formed on both end sections in the axial direction of the middle section in the circumferential direction of each of the column sections 16. A front support plate section 19 that protrudes outward in the radial direction from the outer-circumferential surface of each column section 16 is formed in the center section in the axial direction of the portion a little further near the front in the circumferential direction (left in FIG. 13 and FIG. 14) than the rear support plate sections 18 of the column sections 16. Pockets 21 are provided in the portions surrounded on four sides by the pair of rim sections 15 and a set of two column sections 16 that are adjacent in the circumferential direction, and the rollers 9 are arranged in these pockets so as to be able to roll, and to move a little in the circumferential direction.
On the other hand, springs 11 for pressing the rollers 9 in the forward direction in the circumferential direction (left direction in FIG. 13) toward the shallow side of the concave sections 14 are provided at plural locations in the circumferential direction of the retainer 10 between the retainer 10 and the rollers 9. The springs 11 are obtained by performing a bending process on stainless steel plate (elastic metal plate) such as SUS304. The springs 11, as illustrated in FIG. 14 have an overall C shape along three sides of a trapezoid, and respectively have a flat plate shaped base section 22, a pair of elastic pressure sections 23 that are formed by bending the portions on both sides in the length direction of the base section 22 at acute angles (θ1) to one side in the thickness direction (left side in FIG. 14) of the base section 22, and a pair of elbow sections 24 that are provided in the continuous sections between the pair of elastic pressure sections 23 and the base section 22. The base section 22 has the function of securing the spring 11 to the retainer 10, the elastic pressure sections 23 have the function of elastically pressing the roller 9 by the tip-end sections, and the elbow sections 24 have a function of allowing the elastic pressure sections 23 to elastically bend with respect to the base section 22.
Each of the springs 11 is secured to the retainer 10 by bringing the front side surface of the base section 22 (left side surface in FIG. 13 and FIG. 14) in elastic contact with the rear side surface (right side surface in FIG. 13 and FIG. 14) of the support plate section 19, and bringing both end sections of the rear side surface (right side surface in FIG. 13 and FIG. 14) of the base section 22 in elastic contact with the front side surface (left side surface in the FIG. 13 and FIG. 14) of the pair of rear support plate sections 18. Moreover, in this state, protruding sections 20 are arranged on the inner side of the pair of elbow sections 24 that exist between the base section 22 and pair of elastic pressure sections 23 of the springs 11.
With the springs 11 secured to the retainer 10, the tip-end sections of the pair of elastic pressure sections 23 come in elastic contact with the rolling surfaces (outer-circumferential surfaces) of the rollers 9. The rollers 9 are elastically pressed by the elastic pressure sections 23 forward in the circumferential direction toward the portion of the cylindrical space between the cylindrical surface 12 and cam surface 13 having a narrow width in the radial direction. As a result, during operation, switching between the locked state and the overrun state of the roller clutch 5 is performed quickly.
In the pulley apparatus 1 equipped with a roller clutch, when the follower pulley 3, around the inside of which the clutch outer ring 8 is fitted and fastened, rotates with respect to the sleeve 2, around which the outside of which the clutch inner ring 7 is fitted and fastened, in the same direction that the springs 11 press the rollers 9 (forward direction in the circumferential direction), a force acts on the rollers 9 from the cylindrical surface 12 and cam surface 13 in the same direction as the pressure direction. As a result, the rollers 9 move toward the portions of the cylindrical space where the width in the radial direction is narrow, and are driven into these portions in a wedge shape. As a result, a state occurs in which torque can be transmitted between the sleeve 2 and the follower pulley 3 (locked state), and the sleeve 2 and follower pulley 3 rotate in synchronization.
On the other hand, when the follower pulley 3 rotates in the opposite direction of the pressure direction (toward the rear in the circumferential direction), a force in the opposite direction of the pressure direction acts on the rollers 9 from the cylindrical surface 12. As a result, there is a tendency for the rollers 9 to move toward the portions of the cylindrical space where the width in the radial direction is wide. When this occurs, the rollers 9 causes the elastic pressure sections 23 of the springs 11 to bend. The rollers 9 that move toward the portions having the wide width are able to freely roll and move a little in this portion. As a result, a state occurs in which torque is unable to be transmitted between the sleeve 2 and follower pulley 3.
The pulley apparatus 1 equipped with a roller clutch is such that the sleeve 2 is fitted around and fastened to the end section of the rotating shaft of an auxiliary machine such as an alternator, and a continuous belt is placed around the outer-circumferential surface of the follower pulley 3. This continuous belt extends around a drive pulley that is fastened to the end section of the crankshaft or the like of an engine, and is driven by the rotation of the drive pulley. When the operating speed of the continuous belt is constant or increasing, the roller clutch 5 is connected and set to the locked state, and torque can be transmitted to the rotating shaft from the follower pulley 3. On the other hand, when the operating speed of the continuous belt is decreasing, the connection of the roller clutch 5 is released and set to the overrun state, in which the follower pulley 3 freely rotates relative to the rotating shaft. As a result, even when the rotational angular velocity of the crankshaft changes, a decrease in life of the continuous belt due to wear and the occurrence of abnormal noise called squealing are prevented, and a decrease in the generating efficiency of the alternator is also prevented.
In the roller clutch 5, the circumferential surface 12 and the cam surface 13 that come in contact with the rollers 9 may be formed directly on the inner-circumferential surface of the follower pulley 3 and the outer-circumferential surface of the sleeve 2. Moreover, as illustrated in FIG. 15, the arrangement in the radial direction of the cylindrical surface 12 and cam surface 13 may also be opposite from that described above. In other words, in a case in which operation in the overrun state is performed a lot of the time, and the amount of time in which operation is performed in the locked state is much shorter when compared with the overall operating time such as when assembled on the end section of a drive shaft of a starter motor or the like, preferably the cam surface 13 is formed on the inner-circumferential surface of the clutch outer ring 8a, and the cylindrical surface 12 is formed on the outer-circumferential surface of the clutch inner ring 7a. When the arrangement in the radial direction of the cylindrical surface 12 and the cam surface 13 is opposite in this way, the centrifugal force that occurs when rotating in the overrun state moves the rollers 9 back into the concave sections 14, and makes it possible to easily prevent rubbing between the rolling surfaces of the rollers 9 and the cylindrical surface 12.
However, in the case of this first example of roller clutch 5 having conventional construction, from the aspect of preventing the rollers 9 from becoming skewed, and keeping stress that occurs in the springs 11 low, there is still room for improvement. In other words, as illustrated in FIG. 16, the pair of elastic pressure sections 23 of the spring 11 are provided so as to extend in directions closer to each other toward the tip-end sections over the entire length thereof. Therefore, the space between the pair of elastic pressure sections 23 becomes the shortest between the tip-end sections that come in contact with the roller 9. In other words, the distance X1 between the force points of the elastic pressure sections 23 becomes short, and the tip-end sections of the elastic pressure sections 23 come in contact with the portions of the rolling surface of the roller 9 that are comparatively close to the center section in the axial direction, so it is easy for the roller 9 to become skewed due to the pressure force of the elastic pressure sections 23. Moreover, it is difficult to keep the overall length of the elastic pressure sections 23 long, so the distance Y1 (distance in the direction that is orthogonal to the direction of the line of action of force from the roller 9) from the force point A1 at the tip-end section of the elastic pressure sections 23 where a force from the roller 9 acts to the fulcrum point B1 (area of contact between the front-side surfaces of the end sections of a pair of rear support plate sections 18 and the rear-side surfaces of both end sections of the base section 22) that is the portion that supports force acting on the elastic pressure sections 23 becomes short. Therefore, the amount of bending (bending angle) of the elastic pressure sections 23 becomes large, and it becomes easy for the stress that occurs in the elbow sections 24 to become high.
On the other hand, JPH11093984 discloses construction of a spring in which the distance between the force points can be made large. FIG. 17 and FIG. 18 illustrate another example of a roller clutch 5a that has this kind of spring. In this construction, the spring 11a of the roller clutch 5a is obtained by bending stainless steel plate into an arc shape. The center section in the lengthwise direction of the spring 11a is taken to be the base section 22a, and the remaining portions except for the base section 22a (center section) are taken to be a pair of elastic pressure sections 23a. The base section 22a comes in contact with the side surface in the circumferential direction of the column sections 16a of the retainer 10a, and the tip-end sections of the elastic pressure sections 23a coming in elastic contact with the rolling surface of the roller 9.
With this construction, as illustrated in FIG. 18, the elastic pressure sections 23a extend in a direction going away from each other from the base section 22a toward the tip-end sections. Therefore, the distance X2 between force points, which is the space between the tip-end sections 23a of the elastic pressure sections 23a, can be made sufficiently large when compared with the construction illustrated in FIG. 16 (X2>X1). Therefore, it becomes possible for the tip-end sections of the elastic pressure sections 23a to press the portions near both ends in the axial direction of the rolling surface of the roller 9, and thus it is possible to keep the roller 9 from becoming skewed. However, in this construction as well, the distance Y2 from the force point A2, which is the tip-end section of the elastic pressure sections 23a, 23a, to the fulcrum point B2 (base section 22a) that supports the force acting on the elastic pressure sections 23a is not sufficiently long. Therefore, the problems of the amount of bending of the elastic pressure sections 23a becoming large, and the stress that occurs in the base end sections of the elastic pressure sections 23a becoming high are not eliminated.